Railroad tank car



Oct. 11, 1966 F. w. SCHWARTZ, JR, ETAL 3,277,842

RAILROAD TANK CAR 2 Sheets-$heet 1 Filed Aug. 24, 1962 INVENTGRS Frederick Schwartz Jr Roberf E Sen? ym), @440 my.

United States Patent 3,277,842 RAILROAD TANK CAR Frederick W. Schwartz, .Ir., Clarendon Hills, and Robert F. Seitz, Hazel Crest, 11]., assignors to Union Tank Car Company, a corporation of New Jersey Filed Aug. 24, 1962, Ser. No. 219,197 12 Claims. (Cl. 105-358) This invention relates to railway rolling stock, and more particularly to improved container structure for tank cars.

To ensure safe handling, the Interstate Commerce Commission and the Association of American Railroads have established regulations specifying such things as shell thickness, material, and maximum for internal pressure, weight, length, width, height, center of gravity location, track clearance, and certain ratios between such dimensions for railroad vehicles. The effect of these regulations is to determine the shapes in which a tank car can be made.

A tank car should be made from relatively thin metal in order to minimize Weight and reduce manufacturing expense by permitting use of economical shaping techniques such as rolling. However, when a tank car operates at internal pressures greater than atmospheric, thin metal can be used only when the tank has a shape that resists pressurecaused stresses, or when the tank sides are adequately reinforced. Heretofore, the result has been that pressurized tank cars conforming to the abovementioned regulations have been constructed with capacities only up to about 30,000 gallons; these cars have had the general configuration of right circular cylinders.

Attempts have been made by the prior art to provide large capacity pressurized tank cars in excess of 30,000 gallons that satisfy the above-mentioned regulations. However, the prior art arrangements were expensive to produce and limited to about 35,000 gallons in the maximum volumetric capacity attainable. For example, tank cars having the configuration of two cones with coinciding bases, or the configuration of .a cylinder with cones attached to its ends have been proposed. These configurations are unsatisfactory because they do not efiiciently utilize dimensional allowances provided by the regulations.

Another prior art attempt to provide a large volume tank car involved shaping the car as a rectangular prism with truncated cylinders attached to its top and bottom. This arrangement is not satisfactory for cars having internal pressures above atmospheric pressure because the straight sides of the car had to be connected internally throughout their length by numerous horizontal tie rods at vertically spaced locations. This was necessary to prevent bulging or rupture of the straight portions of the sides when the car was pressurized. Providing numerous internal tie rods at diifering vertical locations greatly increases the cost of the car, and also results in a highly cluttered interior that is difficult to maintain in satisfactory clean condition.

As will be explained in paragraphs that follow, by practicing our invention it is possible to produce from relatively thin metal by relatively economical fabrication techniques, a tank car having a capacity of about 50,000 gallons that is operable at relatively high internal pressures, and to have the car satisfy the regulations governing railroad vehicle size and shape.

Accordingly, it is an object of our invention to provide an improved railroad tank car of large capacity.

Another object is to provide a container tank for railroad vehicles having a cross sectional configuration that elficiently uses the dimensions specified by the agencies regulating the shape and size of railroad cars.

Another object is to provide a container tank for railway vehicles which may be fabricated from relatively thin gauge metal yet still resist high internal pressures.

Another object is to provide a container tank for railway vehicles used at high internal pressures that requires a minimum of internal support for the sides.

Another object is to provide a large capacity container tank for railway vehicles which may be fabricated by relatively inexpensive manufacturing techniques.

Another object is to provide a container for use at high internal pressures wherein the stresses to which the container is subjected in the circumferential direction are essentially only hoop stresses.

A further object is to provide a transition section connecting sections of differing shapes in a high internal pressure container in which binding stresses are substantially eliminated in the shell of the transition section.

A still further object is to provide a large volume container for railroad tank cars which leaves room for the car wheels therebeneath.

Other objects and advantages of our invention will become apparent from the drawings, specification, and claims, and the scope of the invention will be pointed out in the claims.

Briefly stated, according to one aspect of our invention, we provide a container for a railroad tank car wherein a portion of the container has the con-figuration of two lengthwise-truncated intersecting cylinders connected at their lines of intersection. Another aspect of the invention concerns a railroad tank car having a container section in the configuration of two intersecting cylinders and a different container section having the configuration of a single cylinder, and a transition section connecting the two previously mentioned sections wherein the transition section has the configuration of two cylinders that intersect at an angle to each other.

In the drawing:

FIGURE 1 is a schematic perspective view of. an embodiment of a railroad tank car in accord with the teachings of our invention.

FIGURE 2 is a cross sectional view taken along line 2-2 in FIG. 1.

FIGURE 3 is a cross sectional view taken along the line 3-3 in FIG. 1.

FIGURE 4 is a cross sectional view taken along line 4-4 in FIG. 1.

FIGURE 5 is a partially broken-away enlarged side elevational view of a transition section of the container for the tank car of FIG. 1.

FIGURE 6 is a schematic representation of a cylinder having a truncated portion usable to form part of the transition section shown in FIG. 5.

FIGURE 7 is a schematic representation of another cylinder having a truncated portion usable to form another part of the transition section shown in FIG. 5.

FIGURE 8 is a schematic representation showing how a tank car in accord with our teachings satisfies the dimensional requirements of agencies regulating railway transportation.

FIG. 1 shows a schematic representation of a railroad tank car 10 in accord with the teachings of our invention. The car 10 has a commodity container tank 11 having a first or center section 12, substantially identical second or end sections 13, and substantially identical transition section 14, which connect the first section to the end sections. Rounded end caps 15 are provided according to the usual practice. Conventional trucks 16 having wheels 17 are attached to the container 11 by any convenient means, such as a metal cradle structure 18, Conventional coupling devices 19 are provided for connecting the the

ing means 27 and 27'.

cars to each other. The specific construction of the coupling devices, wheeled trucks, and attaching frame structure form no part of the present invention, so they have been schematically illustrated in the drawing. The tank 11 will have suitable inlet and outlet valves, a manway 'and other conventional accessories, but these have not been illustrated because their details are not a part of the invention. Our invention resides in the novel arrangement of the container tank 11.

FIG. 2 shows the cross-sectional configuration of the center section 12 taken in -a plane perpendicular to a lengthwise axis 20 of the car. The expression lengthwise axis, as used in the specification and claims, is intended to mean any axis passing through a right circular cylindrical portion of the tank 11 which is parallel to the center axis of such cylindrical portion. The crosssection is two circles of equal radius intersecting to define substantially identical circular arcs 21 and 22. This is accomplished by constructing the section 12 from two open-ended and substantially identical metal shells 23 land 24, each of which is a truncated portion of a right circular cylinder.

:horizontally spaced tie rods may also be employed without departing from the spirit or scope of the invention.

FIG. 3 shows that end sections 13 have the configuration of a single circle 28 in a plane perpendicular to the lengthwise axis 20. This is accomplished by forming the end sections 13 from metal shells 29 shaped as right circular cylinders. In our preferred embodiment, the circle 28 has the same radius as the are 21, and the longitudinal axes of the circles 28 coincide with that of the arc 21. No internal connecting means is needed in the sections 13 because they are circular in cross-section,

FIG. 4 shows the cross-sectional configuration of the transition sections 14 when taken in a plane perpendicular to the axis 20; the cross-section is two circles intersecting to define substantially identical arcs 31 and 32. This is accomplished by constructing the sections 14 from two open-ended metal shells 33 and 34, which are truncated portions of circular cylinders having radii identical to the radii of arcs 21 and 22; however, the cylinders defining the sections 14 are truncated differently from those defining the section 12, as explained hereafter.

The shells 33 and 34 are joined by welding at points of intersection 35 and 36. The points 35 and 36 lie in a 'plane oblique to the horizontal, and the center lines of the cylinders intersect. The weld seams 35' and 36' are 'connected by means 27, as described with reference to FIG. 2.

When the tank 11 is to be used at internal pressures 'above atmospheric, the shells 33 and 34 should be symmetrical about a line joining the weld seams when viewed in planes perpendicular to a lengthwise axis of the tank 11. The reason is to prevent pressure-caused torques from being exerted on the weld seams and the connect- This configuration obviously exists in section 12 where the shells from which the section is formed are identical. However, the transition sections 14 must vary in shape from the relatively large size at the ends that join the section 12 along the junction lines 38 to the relatively small size at the ends that join the sections 13 along the junction lines 39. This can be accomplished by truncating cylindrical shells in our preferred manner described below with reference to FIG. 5.

FIG. shows that the weld seam 36' is a line extend- 7 ing from the point 40, which represents the end of the weld seam 26' at the junction line 38, to the point 41,

which represents the intersection of the plane defined by horizontal diameters of the cylindrical shell 29 and the junction line 39. Thus the weld seams joining the shells 33 and 34 define a plane oblique to the horizontal. The upper shell 33 is, in effect, a continuation of the shell 23, except that the bottom thereof is gradually sliced away along the seam 36' until it merges with the top half of the shell 29. The locus of the centers of the shell 33 is'the dotted line 43, which is also the locus of the centers of shells 23 and 29. The line 43 crosses the junction line 39 in the plane of the point 41, and crosses the plane of the junction line 38 a vertical distance d spaced above the point 40, The distance d is also the vertical spacing between seam 26' and the centers of the circles defined by the shells 23 and 24.

The bottom shell 34 varies in shape from the junction line 38, where it is identical to the shell 24, to the junction line 39, where it is identical to the lower half of the shell 29. The dotted line 44 is the locus of centers of the shell 34. The line 44 crosses the line 39 in the horizontal plane of the point 41, and crosses the plane of the line 38 at the vertical distance at below the point 40. This arrangement causes the spacing between seam 36' and the center of any circle defined by the shell 34 intersecting a plane perpendicular to the lengthwise axis 20 of the tank 11 to be the same as the spacing between the seam 36 and the center of the circle defined by the shell 33 and the same plane. This means that the crosssection of the shell 33 is identical to the cross-section of the shell 34 in any plane perpendicular to a lengthwise axis of the tank. This will result in essentially no internal pressure-caused torque being exerted on the weld seams and connecting means 27 and 27' when the tank is pressurized.

FIGS. 6 and 7 illustrate one way in which the metal shells 33 and 34 can be fabricated economically. The shell 33 can be made from a sheet of metal rolled to the shape of a right circular cylinder 50 that is truncated by a plane 51. The plane 51 cuts one end of the cylinder 50 at its center line 52; the plane 51 cuts the other end of the cylinder 50 at the distance d from its center line 52.

The shell 34 can be made from a sheet of metal rolled to the shape of a cylindroid 53 that is truncated by a plane 54. The cylindroid 53 is a circular cylinder whose center line 61 is not perpendicular to its base. The plane 54 cuts one end of the cylindroid 53 at its center line 61, and the plane 54 cuts the other end at the distance d from the center line 61.

The distance d and length l in FIGS. 6 and 7 are intended to represent :the distance d and length l in FIG. 5.

It can be shown that the acute angle between the center line 61 of the cylindroid 53 and its base is equal to -a,

where Referring to FIG. 5, the angle a is obviously equal to the angle between the lines 43 and 44. Line 43 is perpendicular to the plane of the junction line 38, which represents the base of the cylindroid defining shell 34. Therefore, the angle between the lines 43 and 44 and also the angle a is equal to Where a' equals the vertical distance in the plane of the line 38 between the center line 44 of the shell 34 and the weld seam 36', and l equals the length of the shell 34 in the direction perpendicular to its base (i.e., between the junction lines 38 and39).

When the cylinders 50 and 53 in FIGS. 6 and 7 have the same radius and when the center line of the cylindroid 53 intersects its base at an angle 5 as defined above, the truncated portions (i.e., the sections that are not cross hatched) will mate to form a transition section as described with reference to FIG. 5.

vfor vessels carrying heavy commodities which exert large forces against the sides and bottom of the car. The reason is that straight line sides would buckle or bulge outwardly under the high pressure or the weight of the commodity carried. To prevent this, the straight sides would have .to be internally connected at numerous locations, as for example by placing tie rods across the interior of the car. This is not practical because of the expense involved and because of the difliculty of cleaning and otherwise maintaining numerous rods or other structure on the interior of the car. Another alternative would be to reinforce the straight sides with external stifiening structures. However, this is undesirable because it would reduce the area in the outline 70 available for volumetric capacity.

Tank cars built as right circular cylinders obviate the above difliculty because internal pressures cause only hope stresses in the circumferential direction. However, the circle 71 represents :the maximum cross section permissible for such a cylindrical tank car. It is obvious that this wastes a great deal of space that could be used tocarry a commodity. For example, the theoretical maximum volume of a tank car having a generally right circular cylindrical configuration to be used for liquid propane transportation would have to be less than about 36,000 gallons in order for the car to satisfy the regulations.

By the practice of our invention, the otherwise wasted space is made usable by intersecting the circle 72 with the circle 71 to define the cross section of the car. The cross sectional area added by the circle 72 represents the additional volume attainable in a tank car constructed in accord with our teachings. For example, a tank car for liquid propane transportation having a volume of about 50,000 gallons could be made and still satisfy the regulations. The approximate dimensions of such a car would be as follows:

Length of center section 12 inches 402 Length of each end section 13 do 113 Length of each rounded end cap 15 do 27 Length of each transition section 14 do 176 Radius of each circular shell do 54 Spacing d do 22 Angle 1428 The material used would be ASTM-2l2, grade B, flange quality steel; the tank walls would be inch thick, and the connecting plates 27 and 27 would be inch thick. Such a car could be operated at pressures up to about 255 p.s.i.

Those skilled in the art will realize that slightly more volume could be added as represented by the areas 73 in FIG. 8 by making the sides of the tank car straight cusps 75 where the circles intersect. The small amount of volume lost as represented by the area 73 becomes insignificant when balanced against the advantages of making the tank in a shape in accord with our teachings.

It has thus been shown that by practicing our invention, a railroad tank car can be fabicated by relatively inexpensive techniques from relatively thin metal and yet Withstand high internal pressures with a minimum of internal support for the car sides. The reason for this is that essentially the only stresses in the circumferential direction to which the sides of the tank car are subjected when it is under high internal pressure are hoop stresses. Hoop stresses are those which act on the sides of a circular vessel in such a manner that they tend to increase its circumference. Stresses other than hoop stresses would occur at the weld line seams, (i.e., the cusps 75) if internal connecting means such as 27 and 27' were not employed. The connecting means balances the horizontal components of hoop stress at the cusps 75, and when the shells are symmetrical about the plane of the connecting means, the vertical components of hoop stress balance each other. Thus, only hoop stresses remain in the shells forming the transition section.

The result is that the tank shells can be made from relatively thin metal which in turn means that the metal can be contoured to shape by relatively inexpensive fabrication techniques, such as rolling. Furthermore, our unique transition section makes efiicient use of available space to provide additional container volume while leaving space for the wheels and associated structure. Therefore, tanks cars made in accord with our teachings provide optimum "balance between the need for maximum size and maximum strength with minimum weight and minimum fabrication cost, while satisfying railroad vehicle size and shape regulations.

It will be understood, of course, that while the forms of the invention shown and described constitute preferred embodiments thereof, it is not intended herein to illustrate all of the equivalent forms or ramifications thereof. It will also be understood that the Words used are words of description rather than of limitation; for example, words such as horizontal and vertical are intended to be used in their relative sense, since they would otherwise become meaningless when referring to a tank car travelling up or down a steep slope. Various changes may be made without departing from the spirit of the invention herein disclosed, and it is aimed in the appended claims to cover all such changes as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In a large volume railroad car having a first tank section having a wall in the configuration of two equal radius substantially identical parallel-axis intersecting right circular cylinders each of which is greater than a Semi-circle in cross section, and a second tank section having a wall in the configuration of one complete right circular cylinder of the same radius as the previously mentioned cylinders, the improvement in means connecting said first and second sections comprising a transition tank section joined at one end to said first section and joined at its other end to said second section, said transition section having an upper wall portion comprising a truncated right circular cylinder and a lower wall portion comprising a truncated cylindroid, the last mentioned cylinder and said cylindroid each having the same radius as said previously mentioned cylinders, and the angle that the center line of said cylindroid forms with its base being equal to 'where l is the length between said ends of said transition than a semi-circle in cross section, and an end tank section having a wall in the configuration of a single cylinder aligned with the uppermost of the cylinders of said main tank section, a transition tank section connecting said main and end tank sections comprising a metal shell having a wall in the configuration of a truncated right circular cylinder aligned with said single cylinder, said right circular cylinder being joined at its edges to the edges of a metal shell having the configuration of a difierently truncated cylinder, and said metal shells defining said transition tank section having a configuration mating with that of said main tank section at the end connected thereto and having a configuration mating with that of said end tank section at the end connected thereto, whereby the volume of said tank sections is greater than that of a cylinder of equal length having a radius equal to that of the largest of said walls.

3. A large volume railroad tank car for operation at an internal pressure greater than atmospheric pressure comprising a first tank section having a Wall in the configuration of two identical substantially parallel axis right circular cylinders interstecting in a substantially horizontal plane, each of said parallel cylinders being greater than a semi-circle in cross section, a second tank section having a wall in the configuration of a single cylinder, a transition tank section connecting said first and second tank sections, said transition tank section having a wall in the configuration of two intersecting cylinders, the cross section of said transition tank section in a plane perpendicular to a longitudinal axis of said tank car being two substantially identical circular arcs, and means respectively connecting the cylinders defining said first tank section and the cylinders defining said transition tank section at their lines of intersection, whereby the volume of said tank sections is greater than that of a cylinder having an equal length and having a radius equal to that of the largest of said walls.

4. A railroad tank car as defined in claim 3 in which the last mentioned means comprises perforated plate means.

5. In a large volume railroad tank car, a main container portion having a wall comprising a pair of lengthwise truncated cylindrical metal shells of uniform radius, the cross section of each shell being a circular are greater than a semi-circle, said shells being aligned with open sides facing each other and welded together along their edges, the weld joints lying in a substantially horizontal plane, means spanning the interior of said container portion connecting said weld joints across said open sides, and the centers of said shells being spaced apart vertically equal distances above and below said plane, whereby the volume of said container portion is greater than that of a cylinder of equal length and radius.

6. In a large volume railroad tank car, a main container portion having a wall in the configuration of two horizontally intersecting cylinders, each of which is greater than a semicircle in in cross section, a spaced end container portion having a wall in the configuration of a single cylinder, and a transition container portion connecting the spaced main and end container portions comprising a pair of lengthwise truncated cylindrical metal shells aligned with open sides facing each other and welded together along their edges, the weld joints lying in a plane oblique to the horizontal, and means spanning the interior of said transition container portion connecting said weld joints across said open sides, and said transition container portion having a configuration mating with that of said main container portion at the end connected thereto and having a configuration mating with that of said end container portion at the end connected thereto, whereby the volume of said container portions is greater than that of a cylinder of equal length and having a radius equal to that of the largest of said walls.

7. A large volume railroad tank car comprising, container means having a main section, an end section, and

a transition section connecting said main and end sections, the respective cross sections of the walls of said sections when viewed in a plane perpendicular to a lengthwise axis of said tank car being substantially as follows:

(a) the said Wall of main section having the configuration of two circles intersecting in a horizontal plane to define two identical arcs, each of which is greater than a semi-circle,

(b) the wall of said end section having the configuration of a circle,

(c) the wall of said transition section having the configuration of two circles intersecting in a plane oblique to the horizontal to define two identical arcs, and said transition section having a configuration mating with that of said main section at the end connected thereto and having a configuration mating with that of said end section at the end connected thereto, whereby the volume of said container means is greater than that of a cylinder of equal length and having a radius equal to that of the largest of said walls.

8. A large volume railroad tank car comprising a main tank section having a wall in the configuration of two intersecting cylinders each of which is greater than a semicircle in cross section, an end tank section having a wall in the configuration of a single cylinder, a transition tank section connecting said main and end tank sections, said transition tank section having a wall in the configuration of two intersecting cylinders, the cross section of said transition tank section in a plane perpendicular to a lengthwise axis of said tank car being two curved arcs each of which decrease in length as said end tank section is approached, and said transition section having a configuration mating with that of said main section at the end connected thereto and having a configuration mating with that of said end section at the end connected thereto, whereby the volume of said tank sections is greater than that of a cylinder of equal length and having a radius equal to the largest of said walls.

9. A large volume wheeled vehicle having a container for operation at internal pressures greater than atmospheric pressure comprising main tank means having a wall portion in the configuration of two substantially identical parallel-axis right circular cylinders intersecting in a substantially horizontal plane, each of said cylinders being greater than a semi-circle in cross section means in said plane connecting said cylinders at their lines of intersection and said axes being spaced apart vertically equal distances above and below said connecting means whereby the volume of said container is greater than that of a cylinder of equal length and having the same radius as said identical cylinders.

10. A large volume railroad tank car comprising main container means having a wall portion which when viewed in a vertical plane has the configuration of two uniform radius circles intersecting in a horizontal plane to define substantially identical arcs, each are being greater than a semi-circle, and means in said plane connecting said circles at their points of intersection whereby said container means has a volume greater than that of a cylinder of equal length and having a radius the same as that of said circles.

11. A large volume railroad tank car comprising a main tank section having a wall in the configuration of two intersecting cylinders, each of which is greater than a semi-circle in cross section, an end tank section having a wall in the configuration of a single cylinder substantially smaller in cross section than said main tank section, a tapered transition tank section connecting said main and end tank sections, and the cross section of a wall of said transition tank section in a plane perpendicular to a lengthwise axis of said tank car being two curved arcs defined by the intersection with said perpendicular plane of two truncated cylinders which intersect each other obliquely, and said transition tank section having a configuration mating with that of said main tank section at the end connected thereto and having a configuration mating with that of said end tank section at the end connected thereto, whereby the volume of said tank sections is greater than that of a cylinder of equal length having a radius equal to that of the largest of said walls.

12. A large volume railroad tank car having a container for operation at internal pressures greater than atmospheric pressure comprising a central tank portion having a wall in the configuration of two longitudinally truncated equal radius parallel-axis right circular cylinders intersecting in a substantially horizontal plane so as to define circular arcs greater than semi-circles, a perforated plate in said plane connecting said cylinders at their lines of intersection, end tank portions each having a wall in the configuration of a single right circular cylinder longitudinally aligned with the uppermost of said cylinders defining said central tank portion and having a radius equal to that of the last mentioned cylinders, transition tank portions connecting said central tank portion to said end tank portions, said transition tank portions each having a wall in the configuration of a truncated right circular first cylinder of radius equal to and aligned with said end .tank portions intersecting a truncated second cylinder in a plane oblique to said horizontal plane, and a perforated plate in said oblique plane connecting the lines of intersection of said first and second cylinders, whereby the volume of said container is greater than that of a cylinder of equal length and having a radius equal to the largest of said walls.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Publication entitled General American Tank Car Manual, pp. 58 and 59, first edition, dated November 1961.

GATC tank car disclosed on page 21 of Railway Locomotive and Cars, August 1961.

ARTHUR L. LA POINT, Primary Examiner.

LEO QUACKENBUSH, Examiner.

D. E. HOFFMAN, Assistant Examiner. 

10. A LARGE VOLUME RAILROAD TANK CAR COMPRISING MAIN CONTAINER MEANS HAVING A WALL PORTION WHICH WHEN VIEWED IN A VERTICAL PLANE HAS THE CONFIGURATION OF TWO UNIFORM RADIUS CIRCLES INTERSECTING IN A HORIZONTAL PLANE TO DEFINE SUBSTANTIALLY INDENTICAL ARCS, EACH ARE BEING GREATER THAN A SEMI-CIRCLE, AND MEANS IN SAID PLANE CONNECTING SAID CIRCLES AT THEIR POINTS OF INTERSECTION WHEREBY SAID CONTAINER MEANS HAS A VOLUME GREATER THAN THAT OF A CYLINDER OF EQUAL LENGTH AND HAVING A RADIUS THE SAME AS THAT OF SAID CIRCLES. 